You used to be able to get a great little camera called a Flip for about £120. It will film for 2 hours on a charge. Flip disappeared but Sony and Panasonic now do similar cameras. Then you need a plastic windscreen suction mount from www.bikecameras.com. That's what I use. Alternatively, Bike Cameras can supply many other types of camera such as the Go Pro. The problem will always be battery life and total capacity to film. If any reader knows of a continuous loop type car camera that records for a couple of hours then records over the previous recording so you always have the last two hours, please let me know. New laser cameras now allow the police to forensically photograph a crash scene in minutes so long crime scene accident investigations should soon be a thing of the past.